Yanche wrote:gerry_g, has it right. Inverter generators or even UPS inverters work fine with resistive loads, i.e. incandescent light bulbs. Anything else especially inductive loads, i.e., motors, switching power supplies, cause the current drawn not to be in phase with the supplied voltage. Current spikes result, which produces large voltage spikes when there are inductors. These will trigger any protection circuits to the off state. Or if they continue will over time puncture the enamel insulation on your motor windings. Don't use them.
Correct and one must remember that motors with ANY slip present an inductive, out of phase load.
Vintage motor speed controls were simply manually switchable inductors. They work very well preventing surges.
Magnetic amplifiers actually a variable inductor controlled by a small DC current. They are complex to design, manufacture and are heavy, don't even think of it! They are used used for expensive industrial controls and other applications such as theatrical high wattage lighting control. Dimming thousands of watts of stage lighting is not cheap.
Most electronic dimmers and speed controls are actually just electronic switches which "turn on" twice every AC cycle when they expect the sine wave supply to be at the desired voltage level. Since a motor with any slip will be out of phase with the supply, a sine wave inverter will see an abnormally high current and likely cut out. A "modified sine wave" inverter actually produces pulse outputs with a peak voltage that of a sine wave and a pulse width such that the average output is the same as that of a sine wave which varies +- from zero. There is no correct point for an electronic speed control to cut in with modified sine wave supplies.
Electronic switching doesn't hurt modern variable speed air mover fan motors. They have enough inductance to prevent motor damage but will feed back out of phase current. The problem occurs when out of phase load is fed back to inverters (or inverter generators). These have very limited ability to absorb fed back current or supply excess current surges. The MOS switching transistors have an absolute current limit and if not automatically shut down, will fry if overloaded, even if just repetitive very short spikes.
Conventional generators (alternators) are also inductive and are usually absorb switched or out of phase loads without damage. The voltage may drop (or be "dirty") or the engine stall but damage is unlikely.
ANY modern electronic device (computers, TVs..) generally have switching power supplies. They put a "dirty" load on the supply. Again, inverters must be over sized or over designed to handle these types of loads. Computer UPS's are specifically designed to feed switching power supplies in a computer which present capacitive load. Most are modified sine wave (pulse) and thus a very poor choice for motors which are inductive loads.
The above is not fully accurate . A complete description requires advanced electrical engineering knowledge. That just happens to be my profession.
This is a VERY COMPLEX subject. a summary might be - FOR shaded pole motors:
Conventional generators (alternators) GOOD
Inverter generators (unless true sine wave and significantly over sized) BAD